The land dispute case experienced by Ir. Sugandi over Certificate of Ownership (SHM) No. 3747/Pondok Pinang, South Jakarta, demonstrates the abuse of authority by notaries and the weakness of land administration oversight. The land certificate belonging to Ir. Sugandi was unlawfully transferred through the involvement of several notaries, resulting in the issuance of a preliminary sale and purchase agreement, a forged deed of sale and purchase, and ultimately a new certificate under the name of a third party. Furthermore, the certificate was encumbered with a mortgage at a banking institution without applying the prudential principle. This study aims to analyze the validity of land transfers carried out through defective deeds, examine the legal responsibility of the notaries involved, assess the juridical implications of the issuance of the new certificate by the National Land Agency, and evaluate the application of the prudential principle by financial institutions in accepting land rights as collateral. In addition, this study formulates legal protection measures that can be provided to the rightful owner to defend his rights. The results of this study are expected to provide theoretical contributions to the development of civil law and land law, as well as practical implications to strengthen the supervision of notarial practice, land institutions, and banking institutions in order to ensure legal certainty and the protection of land ownership rights in Indonesia.